According to the documents, obtained by TMZ, once her insurance lapsed and was subsequently cancelled she could not update it until 2015.

"Shannen says during the lapse period she didn't regularly visit doctors, which had been her practice," TMZ reports.

Shannen Doherty

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"In March 2015, after getting her insurance back, she went to a doctor and discovered she had 'invasive breast cancer metastatic to at least one lymph node.' She says doctors told her the cancer spread during 2014, when she was uninsured, and she blames her business manager."

Doherty, who split with her manager in 2014, claims that it is now likely she will have to undergo a mastectomy and chemotherapy.

The firm at the centre of the lawsuit has released the following statement in response to Doherty's claims:

"Tanner Mainstain is saddened to learn that Ms. Doherty is suffering from cancer and wishes her a full recovery. However, the claim that Tanner Mainstain caused her to be uninsured, prevented her from seeking medical care, or somehow contributed to her cancer is patently false. Tanner Mainstain will aggressively defend all of Ms. Doherty's claims in court."

Doherty, who was reportedly fired from the set of 90210 for being "difficult" and went on to work on Charmed, has been married to photographer Kurt Iswarienko since 2011.

The actress, who currently has several films due for release, is also in pre-production on Kevin Smith's MallBrats, a sequel to 1995's Mallrats.